llvm dev - May 2011 - [LLVMdev] Change the return type of a function

Hello All,

      I want to change the return type of a function in a Pass(in a module
Pass). I dont want to change any of the arguments of that function.
Assume that, I can handle the returning values properly inside the function.
Please guide me how to do this ?


-- 
Regards,
Gokul Ramaswamy,
Graduate Student,
Department of CSE, IIT Bombay
http://www.cse.iitb.ac.in/~ramaswamy
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On 5/7/11 2:01 PM, Gokul Ramaswamy wrote:
> Hello All,
>
>       I want to change the return type of a function in a Pass(in a 
> module Pass). I dont want to change any of the arguments of that function.
> Assume that, I can handle the returning values properly inside the 
> function. Please guide me how to do this ?
You need to do the following steps:

1) Create a new function with the desired function type.
2) Clone the body of the old function into the new function
3) Find all calls calling the old function and replace them with calls 
to the new function.

This is necessary because a function cannot have its type changed once 
it has been created.

Automatic Pool Allocation adds parameters to functions (which is similar 
to what you need to do).  See MakeFunctionClone() in 
poolalloc/lib/PoolAllocate/PoolAllocate.cpp in the poolalloc project.  Use

svn co http://llvm.org/svn/llvm-project/poolalloc/trunk poolalloc

... to get a copy from SVN.

-- John T.
>
>
> -- 
> Regards,
> Gokul Ramaswamy,
> Graduate Student,
> Department of CSE, IIT Bombay
> http://www.cse.iitb.ac.in/~ramaswamy 
> <http://www.cse.iitb.ac.in/%7Eramaswamy>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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Thanks John for the reply. Ya, I took a similar approach. I cloned the
entire
function using CloneFunctionInto() in Cloning.h.

Now, I am facing a new Problem. I am not able to understand the concept of
ValueToValueMap. I am trying to figure it out by testing it. But I am
getting
errors like "Referring to an argument in another function!". I am not
able
to get
good examples nor good documentation on ValueToValueMap. Can you point
me in the right direction ?


On Sun, May 8, 2011 at 5:06 AM, John Criswell <criswell at illinois.edu>
wrote:
>  On 5/7/11 2:01 PM, Gokul Ramaswamy wrote:
>
> Hello All,
>
>       I want to change the return type of a function in a Pass(in a module
> Pass). I dont want to change any of the arguments of that function.
> Assume that, I can handle the returning values properly inside the
> function. Please guide me how to do this ?
>
>
> You need to do the following steps:
>
> 1) Create a new function with the desired function type.
> 2) Clone the body of the old function into the new function
> 3) Find all calls calling the old function and replace them with calls to
> the new function.
>
> This is necessary because a function cannot have its type changed once it
> has been created.
>
> Automatic Pool Allocation adds parameters to functions (which is similar to
> what you need to do).  See MakeFunctionClone() in
> poolalloc/lib/PoolAllocate/PoolAllocate.cpp in the poolalloc project.  Use
>
> svn co http://llvm.org/svn/llvm-project/poolalloc/trunk poolalloc
>
> ... to get a copy from SVN.
>
> -- John T.
>
>
>
> --
> Regards,
> Gokul Ramaswamy,
> Graduate Student,
> Department of CSE, IIT Bombay
> http://www.cse.iitb.ac.in/~ramaswamy
>
>
> _______________________________________________
> LLVM Developers mailing listLLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>

-- 
Regards,
Gokul Ramaswamy,
Graduate Student,
Department of CSE, IIT Bombay
http://www.cse.iitb.ac.in/~ramaswamy
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